This resource was part of AHRQ's Public Health Emergency Preparedness (PHEP) program, which was discontinued on June 30, 2011, in a realignment of Federal efforts.

This information is for reference purposes only. It was current when produced and may now be outdated. Archive material is no longer maintained, and some links may not work. Persons with disabilities having difficulty accessing this information should contact us at: https://info.ahrq.gov. Let us know the nature of the problem, the Web address of what you want, and your contact information.

Chapter 4. Chlorine

This chapter describes the assumptions for the chlorine scenario, including:

The severity categories.

The arrival pattern of casualties at the hospital(s).

The length of stay by hospital unit (i.e., ED, ICU, and the floor).

The path probability within the hospital(s) and the length of stay.

The overall outcome probabilities (i.e., probability of discharge and probability of death).

The assumed level of resource consumption per patient per day per hospital unit.

Footnotes in the text of a particular section refer to references at the end of the section. In the absence of specific references, parameter estimates were obtained from general references listed in the Hospital Module section.

4.1 Severity Categories

For the chlorine scenario, patients arrive at the hospital(s) in one of two conditions:

Irritated: Burning in eyes or respiratory system, exposed to a detectable odor.

Incapacitated: Intolerable irritation of respiratory system and lungs.

Users have the option of specifying either the number and type or simply the number of casualties who present at their hospital(s).

If the user specifies only the number of casualties, the model assumes the casualties arriving at the hospital(s) are randomly selected from among all casualties from the attack. The distribution of casualty types in this case is as follows:

Casualty Condition

Percent

Irritated: Burning in eyes or respiratory system, exposed to a detectable odor

98.9%

Incapacitated: Intolerable irritation of respiratory system and lungs

1.1%

This breakdown by casualty condition is based on work performed during development of the original Surge Model in 2005. In brief, plume modeling was used to estimate the number of exposed in several different cities. From these data, we developed a model to calculate exposure based upon the population of a given city. Populations were grouped based on high or low exposure with resultant irritation, incapacitation, or death. The percents above represent the percentage of individuals who survive an attack in each condition based upon a city of average size in the United States.

4.2 Casualty Arrival Pattern

For the chlorine scenario, all casualties are assumed to present at the hospital(s) on Day 1.

4.3 Length of Stay By Hospital Unit

The assumed average length of stay (in days) of patients the ED, ICU, and the floor (9) listed at the end of this section) are:

Average Length of Stay by Hospital Unit

Irritated

Incapacitated

ED

1

1

Floor, not via ICU

1

6

Floor, via ICU

1

3

ICU

1

14

4.4 Combined Path Probabilities and Lengths of Stay

The table below shows the assumed probabilities of different "paths" through the hospital(s).

Path

Irritated

Incapacitated

ED → Discharge

0%

0%

ED → Death

0%

0%

ED → Floor → Discharge

90%

0%

ED → Floor → Death

0%

0%

ED → Floor → ICU → Death

0%

0%

ED → Floor → ICU → Floor → Discharge

0%

0%

ED → Floor → ICU → Floor → Death

0%

0%

ED → ICU → Death

0%

0%

ED → ICU → Floor → Discharge

10%

100%

ED → ICU → Floor → Death

0%

0%

The breakdown of length of stay by patient type summed over all paths is:

Average Length of Stay by Patient Outcome

Irritated

Incapacitated

Survivors

2.10

18.00

Fatalities

0.00

0.00

Average Combined

2.10

18.00

4.5 Overall Outcome Probabilities

Based on these inputs, the overall discharge and death probabilities are:

Outcome

Irritated

Incapacitated

Discharge

100%

100%

Death

0%

0%

4.6 Resources Consumed Per Patient Per Day

The assumed level of resource consumption per patient per day (1, 10, 12) listed at the end of this section) is shown in the table below:

a Lambda captures the resource requirement decay rate for a resource. Lambda = 1 implies no decay; the patient requires a constant amount of the resource while s/he is hospitalized. Lambda <1 implies that less of the resource is required each day the patient is hospitalized. Go to section 2.2 for details.